E63 with ESS supercharger and de-catted headers = exhaust smell in cabin at stoplight
(yes, I know this is the E60 forum, but there's more of you guys, especially with superchargers)
I have been chasing this for awhile, using a tubular stethoscope with my car on my lift. The more I weld shut exhaust leaks, or re-tighten the V-band clamps on the de-catted headers (no more leaking sound), the more I smell it as I drive slow or stop a light. I do have stock main cats. It's basically impossible to get a stethoscope up to the header mounting flanges. And even if I could, the stethoscope must be RIGHT on top of the leak to hear it. So, if the headers are loose, or leaking, it would be difficult to diagnose. I do not hear anything obvious with the windows open, driving by a wall--like some huge wooshing leak.
I am thinking something in the Smog air pump system is leaking right into the engine bay and getting sucked in while the car is moving slowly. Can anyone corroborate? It's pretty horrible now, and makes driving the car awful.
Also, I have read about flaps in the trunk for outward venting. Not sure where they are, but if they are deteriorated, I imagine exhaust could get in there as well, but this appears to be being sucked in directly via HVAC, and QUICKLY at a stop. I turn HVAC off and it is greatly minimized, but not eliminated.